package com.cty.kmp;

import java.util.Arrays;

public class kmp {
    public static void main(String[] args) {
        String str1 = "BBC ABCDAB ABCDABCDABDE";
//        String str2 = "BBCb";
        String str2 = "ABCDABD";
        int[] next = kmpNext(str2);
        System.out.println("目标数组" + Arrays.toString(next));
        int index = KMP(str1,str2,next);
        System.out.println("找到目标索引" + index);
    }

    public static int KMP(String str1,String str2,int[] next) {

        for (int i = 0, j = 1;i < str1.length(); i++) {
            while (j > 0 && str1.charAt(i) != str2.charAt(j)) {
                j = next[j - 1];
            }

            if (str1.charAt(i) == str2.charAt(j)) {
                j++;
            }
            if (j == str2.length()) {
                return i - j + 1;
            }
        }
        return  -1;
    }
    public static int[] kmpNext(String dest) {
        int[] next = new int[dest.length()];
        next[0] = 0;
        for (int i = 1, j = 0;i < dest.length();i++) {

            while (j > 0 && dest.charAt(i) != dest.charAt(j)) {
                j = next[j - 1];
            }

            if (dest.charAt(i) == dest.charAt(j)) {
                j++;
            }
            next[i] = j;
        }
        return next;
    }
}
